A Spectroscopic and Photometric Study of the Metal-Poor, Pulsating, Post-AGB Binary HD 46703

TL;DR

This study investigates the binary nature, pulsation, and chemical composition of the metal-poor post-AGB star HD 46703, revealing its orbital characteristics, pulsation period, and evidence of chemical depletion due to dust-gas separation in a circumbinary disk.

Contribution

It provides a detailed spectroscopic and photometric analysis of HD 46703, demonstrating its binary status, pulsation, and chemical depletion pattern linked to dust re-accretion, expanding understanding of post-AGB binary systems.

Findings

HD 46703 is a single-line spectroscopic binary with a 600-day period.

The star exhibits a 29-day pulsation period.

Chemical analysis shows depletion of refractory elements due to dust-gas separation.

Abstract

The metal-poor post-AGB star HD 46703 is shown to be a single-line spectroscopic binary with a period of 600 days, a high velocity of -94 km/s, and an orbital eccentricity of 0.3. Light curve studies show that it also pulsates with a period of 29 days. High-resolution, high signal-to-noise spectra were used for a new abundance study. The atmospheric model determined is T(eff) = 6250 K, log(g) = 1.0, V(t) = 3.0 km/s, and a metal abundance of [M/H] = -1.5. A low carbon abundance and lack of s-process element enhancement indicate that the star has not experienced third dredge-up on the AGB. The sulfur and zinc abundances are high compared with iron, and the chemical abundances show a clear anti-correlation with condensation temperature. The abundance depletion pattern is similar to that seen in other post-AGB binaries, and, like them, is attributed to the chemical fractionation of refractory elements onto dust stored in a circumbinary disk and the re-accretion of volatiles in the stellar atmosphere. The infrared excess is small but the excess energy distribution is very similar to what can expected from a disk. HD 46703 joins the growing list of depleted, post-AGB stars which are likely surrounded by a dusty and stable circumbinary disk.